The Orange Box
$9.99
A measly 10 bucks will get you Half-Life 2, Half-Life 2: Episode One, Half-Life 2: Episode Two, Portal, and Team Fortress 2. Granted, Team Fortress 2 is now free-to-play, but the bundle's still cheaper than buying each game piecemeal. If by some weird fluke you've yet to experience one of the greatest first-person shooters ever – Half-Life 2 – now's the time.

Dungeon Defenders
$7.49
A pleasant mix of tower defense and role-playing game, Dungeon Defenders sets itself apart. The Mac version of the game offers a ton of downloadable-content not available in its console counterpart, primarily in the way of more interesting character classes. Dungeon Defenders is a game best played with a group of friends, and a special 4-pack is available through Steam for $22.49.

Limbo
$2.49
Limbo is a game about dealing with the loss of a loved one. But if that sounds a bit heavy, Limbo's also a tricky puzzle-platformer that looks like it's made of shadow puppets. Developer Playdead's indie darling finally made its way to Mac OS X last December, and now here's your chance to grab it for a super low price. The $2.49 price-tag expires on Thursday, so get to shoppin'.

Portal 2
$9.99
After playing through the original Portal, maybe you're still hankering to test out those spatial reasoning skills. Portal 2 takes all the twisted humor and puzzles of the first game, and wraps it in an even deeper narrative. You can even build your very own Portal 2 puzzles with the Perpetual Testing Initiative, included free with the game.

Tiny & Big: Grandpa's Leftovers
$8.49
Maybe the most adorable game of the year so far, Tiny & Big: Grandpa's Leftovers is a stylized platformer with intriguing new mechanics. Protagonist Tiny can use a laser beam to slice up almost anything in the environment, or propel objects with sticky rockets, opening up new ways to approach traditional obstacles. Also, the game is about reclaiming your grandpa's underwear.

The Dream Machine
$7.49
If you're in the mood for something truly unique, how about an adventure game made entirely of clay and cardboard? The Dream Machine eschews the traditional look of the point-and-click genre, utilizing physical objects to tell its puzzle-filled tale. The first three – of five – episodes are currently available. Probably not for people creeped out by that music video from Tool.

Grand Theft Auto: San Andreas
$3.74
All of the Grand Theft Auto games are under a deeper discount on Steam until Thursday, but they'll remain on sale through July 22. If we had to pick the single greatest game in the series, it's San Andreas by a mile. Grand Theft Auto V – currently in production – will return to the palm tree-lined streets of Los Santos, so it's a perfect time to give the town another visit.

The Binding of Isaac Collection
$4.48
From the mind of Edmund McMillen comes The Binding of Isaac; a dark, retro adventure borrowing heavily from the early days of the Zelda franchise. But unlike Nintendo's beloved series, Binding of Isaac features a naked dude and biblical references. Yes, it's weird – and wonderful. The bundle also includes the "Wrath of the Lamb" DLC and game soundtrack.

Psychonauts
$4.99
Long before Tim Schafer and Double Fine smashed crowd-funding records on Kickstarter, the team released its first game, Psychonauts. Although initially released in 2005, six long years passed until Mac gamers could join Raz and the other kids at Whispering Rock Psychic Summer Camp. The game's humor and enjoyable platforming have held up exceptionally well through the years.

Lone Survivor
$6.49
Post-apocalyptic scenarios are rather abundant in videogames, but Lone Survivor has a slightly different feel. Beyond the old-school visuals, the dark setting provides a sense of claustrophobia, elevating questions as to whether or not the protagonist is really all-there, mentally. If you're a fan of survival horror or exploratory adventure games, Lone Survivor is not to be missed.

Star Wars: Knights of the Old Republic
$5.99
Unfortunately, it appears BioWare is going through a hard time with its Old Republic MMO. But years ago, Knights of the Old Republic forged new ground for role-playing games, laying the groundwork for future BioWare titles like Mass Effect. The game's showing its age a bit, but it's still a thoroughly enjoyable adventure through the early Star Wars universe.